Memoirs of a QWERTY Keyboard
Alright, so you’ve got here; you’ve got to 2010; its been roughly five years since you bought that fascinating brick. Now what?
If you’re here and you don’t have a Nokia 6681, continue your journey across the web. This post is strictly for people who’ve been messed up in their minds about buying a newer phone, cause everyone else seems to be getting one of those shiny new S60s or Androids.
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This article is an introduction to the PyQt GUI Application Development Framework that uses Python and Nokia’s Qt.
Ever wondered how to easily write good programs using Python? Programs that would run on any platform – from Windows to Mac OS X along with the various Linux variants? Programs that look good, look native, and also work great?
Here’s one solution – PyQt! With it you can create complete, working applications that may look like this:
Nokia’s Qt is a free (LGPL) cross-platform C++/Java based application-framework, with GUI being its most prominent feature.
PyQt is simply a python-binding to the C++ libraries that Qt provides. Using PyQt one can write neat looking GUI applications that do a lot, and do so easily.
A series of articles, starting with this one will aim to tutor interested programmers into using this wonderful library, and developing applications with it.
The most-minimal pre-requisites are:
Two primary resources where we start from:
Downloading and installing PyQt is fairly easy on Linux thanks to the various package managers. Do check out the download links at each of the above-mentioned links to get them on other platforms as well. Installation help is also provided by Riverbank Computing to help you set-up the PyQt4 library on your OS.
So let’s start off in the same style as almost everything do in a programmer’s perspective: Hello World!
Below is a well documented program for the same:
import sys # Importing the necessary Qt classes. from PyQt4.QtGui import QLabel, QApplication # We use the from foo import * syntax here because # all of Qt's objects begin with a Q # and thus we shouldn't run into namespace problems. if __name__=='__main__': App = QApplication(sys.argv) # All Qt programs need an # QApplication instance. # We pass the sys.argv as its arguments # because Qt is adept at handling some # of the default command-line options # like style, size, etc by itself. Label = QLabel( "Hello World!" ) # QLabel is the class providing a # simple label Label.show() # Like in most GUI toolkits, we have # to manually set it to show App.exec_() # Notice the _ after exec, this is to # avoid the confusion with Python's # exec() built-in-function # exec_() starts the main application # loop. Something like main() of other # toolkits.
This is how it looks when run, a simple application that displays some popular text:
The first thing we have initialized under our ‘__main__’ is the QApplication instance, App. Every GUI application needs this instance to be present. It handles the look and feel of the application and is the main thread of the same. Without it Qt will error out and not run any GUI.
Next we create a label. A label is a simple text-displaying widget used in many forms to describe the input fields and other things. In Qt, its called the QLabel and resides under the QtGui namespace. We create one with a simple Hello World text under the object name Label.
Now we call the show() method of the label so that it appears on the screen. This method is applicable to all QWidget-class children, and QLabel is one among them. Calling show() draws the label widget’s window on the screen.
Finally, we start the application loop, the one responsible for making an application run as an infinite loop waiting for user-interaction. Its done by the exec_() method of QApplication (App is the instance name). Note the _underscore_ in the function name, this is to avoid confusion between Python’s own exec() built-in-function.
With the onslaught of these micro-blogging sites I just can’t think of writing anything more than 140 characters. I’ve tried posting a digest of the same in the blog every week just to keep it going here but it does not look so neat. The Lifestream plug-in, now in action at one of my pages, keeps track of most of the 2.0 updates while I try to bring myself back to posting proper web logs.
With the model exams over, I have about a month’s holidays to prepare for the 6th semester exams. Too much time, probably cause I listen in the classes. This semester was pretty good compared to the five before since it had two programming and one cryptography topic accompanied with some mathematics to keep the dullness taking over. I don’t know what they’ve chosen as electives for the next semester, but I do know that learning Compilers and related topics at college has nil possibility now. I can learn things myself but I don’t always have that discipline required, hence the sadness of not being taught.
I’ve decided to merge here, the PyQt blog I have running over at WordPress.com. I’ve not posted much there, and think that it will be better off at my own blog. Will be posting the existing posts one at a time. Qt 4.5 brings in quite a lot of performance boosts and their blog is very active these days with new concepts/features being put up almost every week. Thank you Nokia!
I also upgraded my Ubuntu from 8.10 to 9.04 flawlessly. The updater’s config-file diff warning notices need to have more options since it blocks the update process; an editor should do well. Jaunty Jackalope, as it is called this time, has good updates like OpenOffice.org 3 (Took long enough), Qt 4.5 (Wonder how KDE4 would perform on this one), Python 2.6 (Deprecation warnings, yum). A lot of other updates are present too, I just mentioned the ones I cared about.
One of my cabinet fans started making very loud droning noises and it made my temper flare quite a few times. I literally punched it, hard. The everlasting dust issue also started to seek attention again and I had no choice but to sit down, yet again, and clean the CPU off its dust. The graphic card had quite a lot of dust collected upon it this time, and that was the reason why the computer whined when I played a graphic-intensive game. After cleaning off the cabinet using an air-blower, I detached the side fans and after discovering that they had a secret compartment beneath the sticker I gave it some oiling.
It does not make much noises now, except for a few audible scratches when my Prescott is really hot trying to run the VisualBoy Advance at 400% throttle. Peace in my small room, at last. I’m losing patience on this 4 year old machine and I have probably mentioned that a hundred times. Yet I can’t seem to take a decision and buy a newer PC, and I don’t know why. The only things am sure about right now is on getting a 22-inch monitor and half a terabyte of secondary storage with two or four gigabytes of primary memory thrown in. The processor and the motherboard, however, are still delaying my decision with new ones coming in every other month. I’m dying to dive into the upgrade pool.
Having, at least, three weeks of free time I decided to get myself the Spider-Man’s Web of Shadows game. It does lack in performance but has some cool moves, like the last movie game did. I also want to play the Broken Sword series again but I don’t think I’ll find time to do that. For now, let’s just swing with the symbiotic.
Anyway, that’s all I’ve done in the past three days. More as they come.
